The term Jacob's staff, also cross-staff, a ballastella, a fore-staff, or a balestilha, is used to refer to several things. This can lead to considerable confusion unless one clarifies the purpose for the object so named. The two most frequent uses are:
- in astronomy and navigation for a simple device to measure angles, later replaced by the more precise sextants;
- in surveying for a vertical rod that penetrates the ground and supports a compass or other instrument.
Read more about Jacob's Staff: Astronomy and Navigation, Surveying
Famous quotes containing the words jacob and/or staff:
“As for me, Abraham, Isaac, and Jacob are now only the subtlest imaginable essences, which would not stain the morning sky.”
—Henry David Thoreau (1817–1862)
“For the first fourteen years for a rod they do whine,
For the next as a pearl in the world they do shine,
For the next trim beauty beginneth to swerve,
For the next matrons or drudges they serve,
For the next doth crave a staff for a stay,
For the next a bier to fetch them away.”
—Thomas Tusser (c. 1520–1580)